Converters are used in many applications for converting electrical energy from one form to another. Converters are used, for example, in connection with solar power. In solar power applications, the converter receives DC voltage from the photovoltaic panels and generally converts it to AC voltage. AC voltage is further fed to the network. In solar power applications, the converter used for converting the voltage is also called a solar inverter.
Converters or inverters utilized in solar and wind power applications are generally placed in containers or similar simple enclosures. These containers are then placed near the actual power generation points. These containers are thus outside in fields or open places which are suitable for the generation of power. The containers or enclosures and the electric components inside the enclosures are cooled using heat exchangers or are cooled directly with air from outside the enclosure.
A solar inverter operates cyclically for natural reasons. In daytime, the inverter is in operation feeding power to the grid. When the sun sets or when the solar panels are not able to generate enough power, the inverter is switched off completely.
The cyclical operation of the inverter causes problems relating to the temperature and humidity inside the enclosure. The temperature inside the enclosure varies considerably and the repeated changes in the temperature cause the semiconductor components to wear out prematurely. Further, the humidity inside the container may cause short circuits. The condensed water may also freeze inside the container, which may block the operation of the converter completely.
It is known to use electric heating to keep the container air dry and warm enough for safe start of the operation. Electricity for such heating is obtained from a separate source of electricity, for example, directly from the mains, when the temperature and/or humidity of the inside air moves to a critical area.
Due to the outside temperature changes, the temperature inside the container varies and the semiconductor lifetime gets shorter due to the temperature cycling.
If the inside air contains humidity, it may condensate without control in the wrong place. Since containers or similar structures enclosing the converter are not airtight, wet air passes easily inside the containers, and the condensed water causes problems which may lead to total breakage of the system.
In very harsh conditions, the temperature inside the container may get considerably below zero degrees Celsius. Normal electronic components are not specified in temperatures which are near −20° C. It is possible that the equipment does not start, or it may get damaged due to the temperature. In such a case, heating is required inside the container for keeping the temperature in allowed limits.